1. Technical Field
The invention relates to a spectacle eyeglass for a myopic child, also called a nearsighted child. It also relates to a process for manufacturing such eyeglass.
2. Description of the Related Art
Many children are concerned with myopia, especially in Asia countries. These children are usually equipped with unifocal negative spectacle eyeglasses, so that they can see sharply objects which are located far away from them, for example at distances longer than 2 m (meter).
But it has been observed that such unifocal myopia correcting equipment, although it compensates for the image defocus on the retina for far objects, does not prevent a long-term increase of the myopia and may even contributes to such myopia increase. Actually, it has been suspected for a long time that the fact that children accommodate a lot at near distance could be one cause responsible for myopia increase.
Then progressive addition eyeglasses suitable for myopia correction have been proposed recently. Studies have demonstrated that wearing progressive lenses during childhood significantly reduces the evolution of myopia. Such eyeglass provides myopia compensation in an upper far vision zone, and also induces reduced accommodation in a lower near vision zone. The dioptric power—also called optical power—varies continuously in a zone of the eyeglass intermediate between the far—and the near vision zones. It has a negative value in the far vision zone, and increases towards less negative values when moving from the far vision zone to the near vision zone. Then, the progressive addition eyeglass provides a good ophthalmic correction to the myopic wearer, while guarantying a reduced level of accommodation when the wearer looks at near located objects through the near vision zone of the eyeglass. In particular, a myopic child who is equipped with such progressive negative eyeglass is lead to accommodate in a smaller extent when looking at near objects, due to the optical power variation of the eyeglass. Thus, such progressive addition eyeglass is believed to reduce the long-term myopia increase for the child-wearer.
However, the inventors have observed that the existing progressive eyeglasses for myopic children were not fully satisfying. Actually, such eyeglasses are not well adapted to children because they have not been designed considering their own particular anatomy and behavior.